1. Field of the Invention
The present invention relates to a semiconductor device. More particularly, it relates to a package structure for housing a ultra-high frequency semiconductor chip.
The package of the ultra-high frequency semiconductor device comprising, for example, a gallium arsenic field effect transistor (FET) used in a giga hetz frequency band should be constructed so that the function of the highly improved semiconductor chip is not degraded and that the package is easily made.
2. Description of the Related Art
A semiconductor device utilizing an FET chip comprises a package for housing the chip, an input lead piece, an output lead piece, and two earth lead pieces for grounding and power supply.
The conventional semiconductor device known to the inventor comprises a semiconductor chip mounted on a ceramic base plate, four ceramic side walls rectangularly arranged surrounding the semiconductor chip, a cap secured to the upper edges of the side walls via a metallized film, an input lead piece and an output lead piece extending from each of the pair of opposing side walls, and two earth lead pieces extending from the other pair of opposing side walls. The earth lead pieces are connected to the semiconductor chip through a metallized film coated on the base plate and side walls.
In the above conventional semiconductor device structure, a satisfactory grounding function has not been obtained since the metallized film is very thin. Also, the characteristic of the device is unstable since unnecessary noise signals are transmitted from the input lead piece to the output lead piece or vice versa through the metallized film coated on the upper edges of the side walls.